The Queen was told directly by her grandson, Prince Harry, that her 11th great-grandchild Lilibet was born.
HELLO! has confirmed that the Duke did speak with his grandmother in advance of yesterday’s announcement.
Harry and his wife Meghan Markle welcomed their second child, daughter Lilibet 'Lili' Diana, on Friday 4 June.
The couple revealed in a statement on Sunday that the name Lili is in honour of Harry's grandmother, the Queen, whose family nickname is Lilibet.
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The pair touched fans with their poignant choice of name for their newborn daughter, but the proud father of two actually hinted at the sweet moniker many years ago.
In 2019, when Meghan was pregnant with the couple's first child, son Archie, the royals visited Birkenhead together, where they spoke to a group of young schoolchildren.
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At the time, Harry expressed an interest in the name 'Lily' asking one mother how she spelled her daughter's flower-inspired name.
Harry has long been close to his grandma
In light of Lilibet's arrival, Prince William and Kate released a statement alongside the Queen, Prince Charles and the Duchess of Cornwall, congratulating the couple on their family of four.
A Buckingham Palace spokesperson said: "The Queen, The Prince of Wales and The Duchess of Cornwall, and The Duke and Duchess of Cambridge have been informed and are delighted with the news of the birth of a daughter for The Duke and Duchess of Sussex."
The pair are already parents to son Archie
Prince William and Kate later added: "We are all delighted by the happy news of the arrival of baby Lili. Congratulations to Harry, Meghan and Archie."
Harry and Meghan's daughter is not the first royal to be born in the US.
The Duke's distant cousin, Lord Frederick Windsor and his wife Lady Frederick Windsor (Sophie Winkleman) welcomed their eldest daughter, Maud Windsor, at the Ronald Reagan UCLA Medical Center in Los Angeles on 15 August 2013.
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